Helio is only with Helio. The Company only uses Services from other phone companys. Helio uses Verizon Wireless, sprint Pcs. So you will always have service. ( this is very true, i have had all wireless service's even prepaid. and helio has never droped a call. ) T-mobile is a GSM network. so you would need to drop them. If you get a helio You will be getting a better service for your money and probly be much happier in life.
This is Bull ive had the helio for about 4 months now and it is the worst. I regret canceling my tmobile plan. I get plenty of drop calls not only that most of the calls go straight into voicemail they never come through the phone.